With consideration to the surge of information on the World Wide Web, it has become essential to keep up with the demand for information put forth by the users of search engines. Current search engines (Google, Yahoo!, Bing) mainly concentrate upon keyword based searches to retrieve relevant results in response to user queries. General purpose search engines introduce a large amount of results. Often, the number of relevant results in the search results is quite small.
For example, users searching for restaurants serving their favorite menu item may enter a search query such as “chicken wings in Orange County”. Such queries may yield a very large number of web pages that the user may have to sort through before identifying a small set of web pages of restaurants in Orange County, that serve chicken wings.
To address the requirement of users to search specific types of content, special purpose search engines exist. Special purpose search engines index only specific types of online content, such as, scholarly publications, patent documents, music and movie content, and so forth. However, such search engines may index a small number of well known online network resources and databases. For instance, a patent search engine may index only the web pages hosted by the various Patent and Trademark Office websites.
Building an index for a special purpose search engine for, say restaurant search, may be time consuming and resource intensive, requiring information such as restaurant names, addresses, telephone numbers, menu served by the restaurants, cuisines, and so forth. The number of restaurants may keep changing with time—with new restaurants being established, and existing ones being shut-down or relocated frequently. Further, the menu offered by these restaurants may also be constantly updated by the restaurants. The restaurants may not have any obligation to reveal such information. Therefore, it is very difficult to index entities, such as restaurants, including associated information such as menu items.